EP0521919B1 - Process for producing a multicoat enamel and aqueous base enamel suitable for said process - Google Patents

Abstract

PCT No. PCT/EP91/00448 Sec. 371 Date Nov. 30, 1992 Sec. 102(e) Date Nov. 30, 1992 PCT Filed Mar. 9, 1991 PCT Pub. No. WO91/14515 PCT Pub. Date Oct. 3, 1991.The invention relates to basecoats for the production of finishes of the basecoat/clearcoat type which comprise a water-thinnable polyacrylate resin which can be obtained by polymerizing, either successively or in part amounts, monomers containing carboxyl groups and monomers free from carboxyl groups in an organic solvent to form a polyacrylate resin which is neutralized, at least partially, and dispersed in water.

Description

• (1) als Basislack ein wäßriger pigmentierter Basislack auf die Substratoberfläche aufgebracht wird
• (2) aus dem in Stufe (1) aufgebrachten Lack ein Polymerfilm gebildet wird
• (3) auf der so erhaltenen Basisschicht ein transparenter Decklack aufgebracht wird und anschließend
• (4) die Basisschicht zusammen mit dem Decklack eingebrannt wird.

The invention relates to a method for producing a multilayer, protective and / or decorative coating, in which

• (1) an aqueous pigmented basecoat is applied to the substrate surface as the basecoat
• (2) a polymer film is formed from the lacquer applied in step (1)
• (3) a transparent topcoat is applied to the base layer thus obtained and then
• (4) the base layer is baked together with the top coat.

This process is the well-known base coat / clear coat process, which is used above all in the automotive industry to produce high-quality top coats, in particular metallic effect coats (see, for example, EP-A-38 127, EP-A-89 497 and DE-OS-36 28 124).

The invention also relates to aqueous paints which are used in the abovementioned. Processes can be used as basecoats.

In the basecoat / clearcoat process in question, basecoats are predominantly used which contain only organic solvents as diluents and / or solvents.

For ecological and economic reasons, the paint industry strives to replace as much of the organic solvent as possible with water. There is a great need for aqueous basecoats which can be used in the basecoat / clearcoat process described above. An essential feature of the basecoat / clearcoat process is that the transparent topcoat is painted onto the not yet baked base layer and only then is the base layer and topcoat baked together (wet-on-wet method).

• (I)
  • (a1) 2,5 bis 15, vorzugsweise 3 bis 7 Gew.-% eines mindestens eine Carboxylgruppe pro Molekül tragenden, mit (b1), (b2), (b3) und (a2) copolymerisierbaren ethy- lenisch ungesättigten Monomeren oder eines Gemisches aus solchen Monomeren zusammen mit
  • (a2) 0 bis 60, vorzugsweise 0 bis 28 Gew.-% eines carboxylgruppenfreien, mit (b1), (b2), (b3) und (a1) copolymerisierbaren ethylenisch ungesättigten Monomers oder eines Gemisches aus solchen Monomeren und
  eine Komponente (b), bestehend aus
  • (b1) 40 bis 90, vorzugsweise 40 bis 80 Gew.-% eines mit (b2), (b3), (a1) und (a2) copolymerisierbaren, im wesentlichen carboxylgruppenfreien (Meth)acrylsäureesters oder eines Gemisches aus solchen (Meth)acrylsäureestern und
  • (b2) 0 bis 45, vorzugsweise 4 bis 34 Gew.-% eines mit (b1), (b3), (a1) und (a2) copolymerisierbaren, ethylenisch ungesättigten Monomeren, das mindestens eine Hydroxylgruppe pro Molekül trägt und im wesentlichen carboxylgruppenfrei ist oder eines Gemisches aus solchen Monomeren und
  • (b3) 0 bis 40, vorzugsweise 10 bis 30 Gew.-% eines mit (b1), (b2), (a1) und (a2) copolymerisierbaren, im wesentlichen carboxylgruppenfreien, von (b1) und (b2) verschiedenen, ethylenisch ungesättigten Monomeren oder eines Gemisches aus solchen Monomeren
  nacheinander oder in Teilmengen alternierend zu einem organischen Lösemittel oder Lösemittelgemisch gegeben werden und in Gegenwart mindestens eines Polymerisationsinitiators polymerisiert werden und
• (II) nach Beendigung der Polymerisation das erhaltene Polyacrylatharz zumindest teilweise neutralisiert und in Wasser dispergiert wird, wobei die Summe der Gewichtsanteile von (a1) (a2), (b1), (b2) und (b3) stets 100 Gew.-% ergibt und (b1), (b2), (b3), (a1) und (a2) in Art und Menge so ausgewählt werden, daß das Polyacrylatharz eine Hydroxylzahl von 0 bis 200, vorzugsweise 20 bis 120, eine Säurezahl von 20 bis 100, vorzugsweise 25 bis 50 und eine Glasübergangstemperatur (T_G) von -40 °C bis +60 °C, vorzugsweise -20 °C bis +40 °C, aufweist.

The object on which the present invention is based is to provide new aqueous lacquers which can be used as basecoats for the basecoat / clearcoat process. This object is surprisingly achieved by the provision of aqueous, pigmented lacquers which are characterized in that they contain a water-dilutable polyacrylate resin which can be obtained by

• (I)
  • (a1) 2.5 to 15, preferably 3 to 7% by weight of an ethylenically unsaturated monomer or a mixture carrying at least one carboxyl group per molecule and copolymerizable with (b1), (b2), (b3) and (a2) from such monomers together with
  • (a2) 0 to 60, preferably 0 to 28% by weight of a carboxyl-free, with (b1), (b2), (b3) and (a1) copolymerizable ethylenically unsaturated monomer or a mixture of such monomers and
  a component (b) consisting of
  • (b1) 40 to 90, preferably 40 to 80% by weight of a (carb) group-free (meth) acrylic acid ester or a mixture of such (meth) acrylic acid esters copolymerizable with (b2), (b3), (a1) and (a2) and
  • (b2) 0 to 45, preferably 4 to 34% by weight of an ethylenically unsaturated monomer copolymerizable with (b1), (b3), (a1) and (a2), which carries at least one hydroxyl group per molecule and is essentially free of carboxyl groups or a mixture of such monomers and
  • (b3) 0 to 40, preferably 10 to 30% by weight of an ethylenically unsaturated, which is copolymerizable with (b1), (b2), (a1) and (a2) and is essentially carboxyl-free, different from (b1) and (b2) Monomers or a mixture of such monomers
  are added in succession or alternately in portions to an organic solvent or solvent mixture and are polymerized in the presence of at least one polymerization initiator and
• (II) after the end of the polymerization, the polyacrylate resin obtained is at least partially neutralized and dispersed in water, the sum of the proportions by weight of (a1) (a2), (b1), (b2) and (b3) always giving 100% by weight and (b1), (b2), (b3), (a1) and (a2) are selected in type and amount such that the polyacrylate resin has a hydroxyl number of 0 to 200, preferably 20 to 120, an acid number of 20 to 100, preferably 25 to 50 and a glass transition temperature (T _G ) of -40 ° C to +60 ° C, preferably -20 ° C to +40 ° C.

The water-dilutable polyacrylate resins used in accordance with the invention enable the formulation of basecoats which - in particular in comparison to known basecoats containing polyacrylate resin - have an increased solids content and a lower tendency to run. In addition, the use of the water-dilutable polyacrylate resins according to the invention, in particular in polyurethane-containing basecoats, leads to stabilization against fluctuating shear stress. Particularly when subjected to weak shear forces, lower or no lowering of viscosity occurs compared to the prior art. This results in improved settling behavior, easier handling and increased application safety.

• 1.) Als Abkürzung für "Methacrylsäure- oder Acrylsäure-" wird gelegentlich (Meth)acrylsäure- verwendet.
• 2.) Die Formulierung "im wesentlichen carboxylgruppenfrei" soll ausdrücken, daß die Komponenten (b1), (b2), und (b3) einen geringen Carboxylgruppengehalt (höchstens aber soviel, daß ein aus den Komponenten (b1), (b2), und (b3) hergestellte Polyacrylatharz eine Säurezahl von höchstens 10 hat) aufweisen können. Es ist aber bevorzugt, daß der Carboxylgruppengehalt der Komponenten (b1), (b2), und (b3) so niedrig wie möglich gehalten wird. Besonders bevorzugt werden carboxylgruppenfreie (b1), (b2), (und (b3) Komponenten eingesetzt.

Before the production of the water-dilutable polyacrylate resins, which are essential to the invention, is described in more detail, two definitions are first given:

• 1.) As an abbreviation for "methacrylic acid or acrylic acid" (meth) acrylic acid is used occasionally.
• 2.) The phrase "essentially free of carboxyl groups" is intended to express that components (b1), (b2), and (b3) have a low carboxyl group content (but at most so much that one of components (b1), (b2), and (b3) produced polyacrylate resin has an acid number of at most 10). However, it is preferred that the carboxyl group content of components (b1), (b2), and (b3) be kept as low as possible. Carboxyl-free (b1), (b2), (and (b3)) components are particularly preferably used.

For the preparation of the polyacrylate resins to be used according to the invention, component (a1) can be any ethylenically unsaturated monomer bearing at least one carboxyl group per molecule and copolymerizable with (a2), (b1), (b2) and (b3) or a mixture of such monomers. Acrylic acid and / or methacrylic acid are preferably used as component (a1). However, other ethylenically unsaturated acids with up to 6 carbon atoms in the molecule can also be used. Examples of such acids are ethacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid. As component (a1) e.g. succinic acid mono (meth) acryloyloxyethyl ester and phthalic acid mono (meth) acryloyloxyethyl ester can also be used.

Any carboxyl-free, ethylenically unsaturated monomer or a mixture of such monomers which is copolymerizable with (b1), (b2), (b3) and (a1) can be used as component (a2). All monomers listed in the description of components (b1), (b2) and (b3) can be used as component (a2).

Component (b1) which can be used is any ester of (meth) acrylic acid or a mixture of such (meth) acrylic esters which is copolymerizable with (b2), (b3), (a1) and (a2) and is essentially free of carboxyl groups. Examples include alkyl acrylates and alkyl methacrylates with up to 20 carbon atoms in the alkyl radical, such as methyl, ethyl, propyl, butyl, hexyl, ethylhexyl, stearyl and lauryl acrylate and methacrylate. Mixtures of alkyl acrylates and / or alkyl methacrylates are preferably used as (b1) components which contain at least 25% by weight of n-butyl or t-butyl acrylate and / or n-butyl or t-butyl methacrylate.

As component (b2), all ethylenically unsaturated monomers copolymerizable with (b1), (b3), (a1) and (a2) which carry at least one hydroxyl group per molecule and are essentially free of carboxyl groups or a mixture of such monomers can be used. Hydroxyalkyl esters of acrylic acid, methacrylic acid or another α, β-ethylenically unsaturated carboxylic acid are mentioned as examples. These esters can be derived from an alkylene glycol esterified with the acid, or they can be obtained by reacting the acid with an alkylene oxide. As component (b2), preference is given to hydroxyalkyl esters of acrylic acid and methacrylic acid, in which the hydroxyalkyl group contains up to 4 carbon atoms, reaction products of cyclic esters, e.g. ε-caprolactone and these hydroxyalkyl esters or mixtures of these hydroxyalkyl esters or ε-caprolactone-modified hydroxyalkyl esters are used. Examples of such hydroxyalkyl esters are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate and 4-hydroxybutyl methacrylate. Corresponding esters of other unsaturated acids, e.g. Ethacrylic acid, crotonic acid and similar acids with up to about 6 carbon atoms per molecule can also be used.

Component (b3) which can be used is all copolymerizable with (b1), (b2), (a1) and (a2), essentially carboxyl-free, from (b1) and (b2) different ethylenically unsaturated monomers or mixtures of such monomers. As component (b3) vinyl aromatic hydrocarbons such as styrene, α-alkyl styrene and vinyl toluene are preferred used.

The polyacrylate resins used according to the invention can be prepared by combining 2.5 to 15, preferably 3 to 7% by weight of component (a1) together with 0 to 60, preferably 0 to 28% by weight of component (a2) to form an organic Solvent or solvent mixture are added, are polymerized there in the presence of at least one polymerization initiator and, after the addition of components (a1) and (a2) has ended, a component (b) consisting of components (b1), (b2) and optionally (b3) is added to the organic solvent or solvent mixture and is polymerized there in the presence of at least one polymerization initiator. The addition of component (b) should only begin when at least 60% by weight, preferably at least 80% by weight, of components (a1) and (a2) have been reacted. It is preferred not to start adding component (b) until components (a1) and (a2) have been substantially completely reacted. After the end of the polymerization, the polyacrylate resin obtained is at least partially neutralized and dispersed in water. The sum of the parts by weight of (a1), (a2), (b1), (b2) and (b3) is always 100% by weight. The components (a1), (a2), (b1), (b2) and (b3) are selected in terms of type and amount such that the polyacrylate resin has a hydroxyl number of 0 to 200, preferably 20 to 120, an acid number of 20 to 100 , preferably 25 to 50 and a glass transition temperature (T _G ) of -40 ° C to +60 ° C, preferably -20 ° C to +40 ° C.

(a1) and (a2) are preferably added to the organic solvent or solvent mixture within 10 to 90 minutes, particularly preferably within 30 to 75 minutes, and there in the presence of at least one Free radical initiator polymerized. Component (b) is preferably added to the organic solvent or solvent mixture within 2 to 8 hours, particularly preferably within 3 to 6 hours, and is polymerized there in the presence of at least one free radical initiator.

The polyacrylate resins to be used according to the invention can also be prepared by alternately adding (a1) and (a2) and component (b) in partial amounts to an organic solvent or solvent mixture and polymerizing there in the presence of at least one free radical initiator. The subsets should each consist of at least 10% by weight of the total amount of component (a1) and (a2) or component (b) to be used. The addition of a partial amount should only begin when at least 60% by weight, preferably at least 80% by weight, of the previous partial amount has been implemented. It is preferred not to start adding a portion until the previous portion has been substantially completely implemented. After the end of the polymerization, the polyacrylate resin obtained is at least partially neutralized and dispersed in water. The sum of the parts by weight of (a1), (a2), (b1), (b2) and (b3) is always 100% by weight. The components (a1), (a2), (b1), (b2) and (b3) are selected in terms of type and amount such that the polyacrylate resin has a hydroxyl number of 0 to 200, preferably 20 to 120, an acid number of 20 to 100 , preferably 25 to 50 and a glass transition temperature (T _G ) of -40 ° C to + 60 ° C, preferably -20 ° C to + 40 ° C.

In a preferred embodiment of this production method, a from 30 to 70% by weight, preferably from 40 to 60% by weight, particularly preferably a portion of component (b) (portion 1) consisting of 50% by weight of the total amount of component (b) to be used added to the organic solvent or solvent mixture and polymerized in the presence of at least one free radical initiator. After the addition of portion 1 has ended, in a second step one of 30 to 70% by weight, preferably one of 40 to 60% by weight, particularly preferably one of 50% by weight of the total amount of mixture to be used from a1) and (a2) existing portion of the mixture of (a1) and (a2) (portion 2) added to the organic solvent or solvent mixture and polymerized in the presence of at least one free radical initiator. After the addition of portion 2 has ended, in a third step one of 30 to 70% by weight, preferably one of 40 to 60% by weight, particularly preferably one of 50% by weight of the total amount of component (b ) existing portion of component (b) (portion 3) is added to the organic solvent or solvent mixture and polymerized in the presence of at least one free radical initiator. After the addition of portion 3 has ended, in a fourth step one of 30 to 70% by weight, preferably one of 40 to 60% by weight, particularly preferably one of 50% by weight of the total amount of mixture to be used is a1) and (a2) existing portion of the mixture of (a1) and (a2) (portion 4) added to the organic solvent or solvent mixture and polymerized in the presence of at least one free radical initiator.

With the addition of subset 2, 3 and 4 should first then be started when at least 60 wt .-%, preferably 80 wt .-% of the preceding subset have been implemented. It is preferred not to start adding a portion until the foregoing portion has been substantially completely implemented.

After the end of the polymerization, the polyacrylate resin obtained is at least partially neutralized and dispersed in water. The sum of the parts by weight of (a1), (a2), (b1), (b2) and (b3) is always 100% by weight. The components (a1), (a2), (b1), (b2) and (b3) are selected in terms of type and amount such that the polyacrylate resin has a hydroxyl number of 0 to 200, preferably 20 to 120, an acid number of 20 to 100 , preferably 25 to 50 and a glass transition temperature (T _G ) of -40 ° C to +60 ° C, preferably -20 ° C to + 40 ° C.

The aliquots 1 and 3 are preferably added within 1 to 4 hours, particularly preferably within 1 1/2 to 3 hours. The aliquots 2 and 4 are preferably added within 5 to 30 minutes, particularly preferably within 7 to 20 minutes.

The organic solvents and polymerization initiators used are the solvents and polymerization initiators customary for the production of polyacrylate resins and suitable for the production of aqueous dispersions. Examples of useful solvents are butyl glycol, 2-methoxypropanol, n-butanol, methoxybutanol, n-propanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether and 3-methyl-3-methoxybutanol called. Free-radical initiators such as benzoyl peroxide, t-butyl perethyl hexanoate, azobisisobutyronitrile and t-butyl perbenzoate are mentioned as examples of useful polymerization initiators. The polymerization is advantageously carried out at a temperature of 80 to 160 ° C, preferably 110 to 160 ° C. The polymerization is complete when all of the monomers used have been essentially completely reacted.

T_G

= Glasübergangstemperatur des Polyacrylatharzes

x

= Anzahl der im Polyacrylatharz einpolymerisierten verschiedenen Monomeren.

W_n

= Gewichtsanteil des n-ten Monomers

T_Gn

= Glasübergangstemperatur des Homopolymers aus dem n-ten Monomer

Die Menge und Zugabegeschwindigkeit des Initiators wird vorzugsweise so gesteuert, daß das erhaltene Polyacrylatharz ein zahlenmittleres Molekulargewicht von 2500 bis 20 000 aufweist. Es ist besonders bevorzugt, die Initiatorzugabe zum gleichen Zeitpunkt wie die Zugabe der polymerisierbaren Komponenten (a1), (a2) und (b) zu beginnen und etwa eine halbe Stunde nachdem die Zugabe der polymerisierbaren Komponenten (a1), (a2) und (b) beendet worden ist, zu beenden. Danach wird das Reaktionsgemisch noch so lange (in der Regel etwa 1 1/2 Stunden) auf Polymerisationstemperatur gehalten, bis alle eingesetzten Monomere im wesentlichen vollständig umgesetzt worden sind. "Im wesentlichen vollständig umgesetzt" soll bedeuten, daß vorzugsweise 100 Gew.-% der eingesetzten Monomere umgesetzt worden sind, daß es aber auch möglich ist, daß ein geringer Restmonomerengehalt von höchstens bis zu etwa 0,5 Gew.-%, bezogen auf das Gewicht der Reaktionsmischung, unumgesetzt zurückbleiben kann.The components (a1), (a2), (b1), (b2) and (b3) are selected in their type and amount so that the reaction product has a hydroxyl number from 0 to 200, preferably 20 to 120, an acid number from 20 to 100 , preferably 25 to 50 and a glass transition temperature (T _G ) of -40 ° C to +60 ° C, preferably -20 ° C to +40 ° C.
The glass transition temperatures of polyacrylate resins can be calculated approximately using the following formula:

T _G

= Glass transition temperature of the polyacrylate resin

x

= Number of different monomers polymerized in the polyacrylate resin.

W _n

= Weight fraction of the nth monomer

T _Gn

= Glass transition temperature of the homopolymer from the nth monomer

The amount and rate of addition of the initiator is preferably controlled so that the polyacrylate resin obtained has a number average molecular weight of 2500 to 20,000. It is particularly preferred to start the initiator addition at the same time as the addition of the polymerizable components (a1), (a2) and (b) and about half an hour after the addition of the polymerizable components (a1), (a2) and (b ) has ended, to end. The reaction mixture is then kept at the polymerization temperature (generally about 1 1/2 hours) until all of the monomers used have essentially been completely reacted. "Substantially completely converted" is intended to mean that preferably 100% by weight of the monomers used have been reacted, but it is also possible that a low residual monomer content of at most up to about 0.5% by weight, based on the Weight of the reaction mixture can remain unreacted.

After the end of the polymerization, the polyacrylate resin obtained is at least partially neutralized and dispersed in water.

Both organic bases and inorganic bases can be used for neutralization. Primary, secondary and tertiary amines, e.g. Ethylamine, propylamine, dimethylamine, dibutylamine, cyclohexylamine, benzylamine, morpholine, piperidine and triethanolamine are used. Tertiary amines are particularly preferably used as neutralizing agents, in particular dimethylethanolamine, triethylamine, tripropylamine and tributylamine.

The neutralization reaction is generally carried out by mixing the neutralizing base with the polyacrylate resin. So much is preferably Base used that the basecoat has a pH of 7-8.5, preferably 7.2 to 7.8.

The partially or completely neutralized polyacrylate resin is then dispersed by adding water. This creates an aqueous polyacrylate resin dispersion. If necessary, part or all of the organic solvent can be distilled off. The polyacrylate resin dispersions according to the invention contain polyacrylate resin particles, the average particle size of which is preferably between 60 and 300 nm (measurement method: laser light scattering, measuring device: Malvern Autosizer 2C).

• (A) 10 bis 95, vorzugsweise 25 bis 70 Gew.-% des erfindungsgemäßen wasserverdünnbaren Polyacrylatharzes,
• (B) 5 bis 50, vorzugsweise 10 bis 40 Gew.-% eines Aminoplastharzes,
• (C) 0 bis 85, vorzugsweise 20 bis 60 Gew.-% eines wasserverdünnbaren Polyesterharzes und
• (D) 0 bis 85, vorzugsweise 0 bis 40 Gew.-% eines wasserverdünnbaren Polyurethanharzes.

Aqueous basecoats according to the invention can be produced with the above-described polyacrylate resins as binders. However, it is preferred to combine the polyacrylate resins with at least one water-thinnable polyurethane resin and / or at least one water-thinnable polyester resin and / or at least one water-thinnable aminoplast resin as a binder. In the case of basecoats which contain only non-metallic pigments or mixtures of non-metallic pigments and no metal pigments, a mixture of is preferably used

• (A) 10 to 95, preferably 25 to 70% by weight of the water-dilutable polyacrylate resin according to the invention,
• (B) 5 to 50, preferably 10 to 40% by weight of an aminoplast resin,
• (C) 0 to 85, preferably 20 to 60% by weight of a water-dilutable polyester resin and
• (D) 0 to 85, preferably 0 to 40% by weight of a water-dilutable polyurethane resin.

The sum of the parts by weight of components (A) to (D) is always 100% by weight.

• (A) 0,1 bis 60, vorzugsweise 1 bis 30 Gew.-% des erfindungsgemäßen wasserverdünnbaren Polyacrylatharzes,
• (B) 0 bis 50, vorzugsweise 5 bis 30 Gew.-% eines Aminoplastharzes,
• (C) 0 bis 50, bevorzugt 15 bis 40 Gew.-% eines wasserverdünnbaren Polyesterharzes und
• (D) 10 bis 99,9, vorzugsweise 20 bis 60 Gew.-% eines wasserverdünnbaren Polyurethanharzes.

In the case of basecoats which contain a metal pigment or a mixture of metal pigments, if appropriate in combination with non-metallic pigments, a mixture of preferably is used as the binder

• (A) 0.1 to 60, preferably 1 to 30% by weight of the water-dilutable polyacrylate resin according to the invention,
• (B) 0 to 50, preferably 5 to 30% by weight of an aminoplast resin,
• (C) 0 to 50, preferably 15 to 40% by weight of a water-dilutable polyester resin and
• (D) 10 to 99.9, preferably 20 to 60% by weight of a water-dilutable polyurethane resin.

The sum of the parts by weight of components (A) to (D) is always 100% by weight.

• (i) ein Polyester- und/oder Polyetherpolyol mit einem zahlenmittleren Molekulargewicht von 400 bis 5000 oder ein Gemisch aus solchen Polyester- und/oder Polyetherpolyolen
• (ii) ein Polyisocyanat oder einem Gemisch aus Polyisocyanaten
• (iii) eine Verbindung, die mindestens eine gegenüber Isocyanatgruppen reaktive und mindestens eine zur Anionenbildung befähigte Gruppe im Molekül aufweist oder ein Gemisch aus solchen Verbindungen
• (iv) gegebenenfalls eine Hydroxyl- und/oder Aminogruppen enthaltende organische Verbindung mit einem Molekulargewicht von 40 bis 600 oder ein Gemisch aus solchen Verbindungen und
• (v) gegebenenfalls eine Verbindung, die mindestens eine gegenüber NCO-Gruppen reaktive Gruppe und mindestens eine Poly(oxyalkylen)gruppe im Molekül aufweist oder ein Gemisch aus solchen Verbindungen

miteinander umgesetzt werden und das entstandene Reaktionsprodukt wenigstens teilweise neutralisiert wird. Das Polyurethanharz sollte zweckmäßigerweise eine Säurezahl von 10 bis 60 und ein zahlenmittleres Molekulargewicht von 4000 bis 25.000 aufweisen.The polyacrylate resins in question can be used, for example, to combine water-dilutable polyurethane resins which can be prepared by

• (i) a polyester and / or polyether polyol with a number average molecular weight of 400 to 5000 or a mixture of such polyester and / or polyether polyols
• (ii) a polyisocyanate or a mixture of polyisocyanates
• (iii) a compound which has at least one group which is reactive towards isocyanate groups and at least one group capable of forming anions in the molecule, or a mixture of such compounds
• (iv) optionally an organic compound containing hydroxyl and / or amino groups and having a molecular weight of 40 to 600 or a mixture of such compounds and
• (v) optionally a compound which has at least one group which is reactive toward NCO groups and at least one poly (oxyalkylene) group in the molecule, or a mixture of such compounds

are reacted with one another and the resulting reaction product is at least partially neutralized. The polyurethane resin should expediently have an acid number of 10 to 60 and a number average molecular weight of 4,000 to 25,000.

The polyurethane resins can be prepared from (i), (ii), (iii), if appropriate (iv) and if appropriate (v) by methods of polyurethane chemistry which are well known to the person skilled in the art (cf., for example, US Pat. No. 4,719,132, DE-OS- 36 28 124, EP-A-89 497, EP-A-256 540 and WO 87/03829).

As component (i), saturated and unsaturated polyester and / or polyether polyols, especially polyester and / or polyether diols with a number-average Molecular weight of 400 to 5000 can be used. Suitable polyether diols are, for example, polyether diols of the general formula H (-0- (CHR 1) _n -) _m OH, where R 1 = hydrogen or a lower, optionally substituted alkyl radical, n = 2 to 6, preferably 3 to 4 and m = 2 to 100, preferably 5 to 50. Linear or branched polyether diols such as poly (oxyethylene) glycols, poly (oxypropylene) glycols and poly (oxybutylene) glycols are mentioned as examples. The selected polyether diols should not introduce excessive amounts of ether groups, otherwise the polymers formed will swell in water. The preferred polyether diols are poly (oxypropylene) glycols in the molar mass range M _n from 400 to 3000.
Polyester diols are produced by esterification of organic dicarboxylic acids or their anhydrides with organic diols or are derived from a hydroxy carboxylic acid or a lactone. To produce branched polyester polyols, polyols or polycarboxylic acids with a higher valency can be used to a small extent. The dicarboxylic acids and diols can be linear or branched aliphatic, cycloaliphatic or aromatic dicarboxylic acids or diols.

The diols used to prepare the polyesters consist, for example, of alkylene glycols, such as ethylene glycol, propylene glycol, butylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and other diols, such as dimethylolcyclohexane. However, small amounts of polyols, such as trimethylolpropane, glycerol, pentaerythritol, can also be added. The acid component of the polyester consists primarily of low molecular weight dicarboxylic acids or their anhydrides with 2 to 30, preferably 4 to 18, carbon atoms in the molecule. Suitable acids are, for example, o-phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, glutaric acid, hexachloroheptanedicarboxylic acid, tetrachlorophthalic fatty acid and /. Instead of these acids, their anhydrides, if they exist, can also be used. Smaller amounts of carboxylic acids with 3 or more carboxyl groups, for example trimellitic anhydride or the adduct of maleic anhydride with unsaturated fatty acids, can also be present in the formation of polyester polyols.

Polyester diols obtained by reacting a lactone with a diol can also be used. They are characterized by the presence of terminal hydroxyl groups and recurring polyester fractions of the formula (-CO- (CHR²) _n -CH₂-0). Here, n is preferably 4 to 6 and the substituent R² is hydrogen, an alkyl, cycloalkyl or alkoxy radical.
No substituent contains more than 12 carbon atoms. The total number of carbon atoms in the substituent does not exceed 12 per lactone ring. Examples include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid and / or hydroxystearic acid.

Unsubstituted ε-caprolactone, in which n is 4 and all R substituents are hydrogen, is preferred for the preparation of the polyester diols. The reaction with lactone can be started by low molecular weight polyols, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, dimethylolcyclohexane. It However, other reaction components such as ethylenediamine, alkyldialkanolamines or urea can also be reacted with caprolactone.

Aliphatic and / or cycloaliphatic and / or aromatic polyisocyanates can be used as component (ii). Examples of aromatic polyisocyanates are phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, biphenylene diisocyanate, naphthylene diisocyanate and diphenylmethane diisocyanate.

Due to their good resistance to ultraviolet light, (cyclo) aliphatic polyisocyanates produce products with a low tendency to yellowing. Examples include isophorone diisocyanate, cyclopentylene diisocyanate and hydrogenation products of aromatic diisocyanates, such as cyclohexylene diisocyanate, methylcyclohexylene diisocyanate and dicyclohexylmethane diisocyanate. Aliphatic diisocyanates are compounds of the formula



OCN- (CR³₂) _r -NCO



wherein r is an integer from 2 to 20, in particular 6 to 8 and R³, which may be the same or different, represents hydrogen or a lower alkyl radical having 1 to 8 carbon atoms, preferably 1 or 2 carbon atoms. Examples include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylethylene diisocyanate, dimethylethylene diisocyanate, methyltrimethylene diisocyanate and trimethylhexane diisocyanate. Isophorone diisocyanate and dicyclohexylmethane diisocyanate are particularly preferably used as diisocyanates.

Component (ii) must be composed in terms of the functionality of the polyisocyanates in such a way that no crosslinked polyurethane resin is obtained. In addition to diisocyanates, component (ii) can also contain a proportion of polyisocyanates with functionalities over two - such as Triisocyanates - included.

Products which have been found to be suitable as triisocyanates are those which result from the trimerization or oligomerization of diisocyanates or from the reaction of diisocyanates with compounds containing polyfunctional OH or NH groups. These include, for example, the biuret of hexamethylene diisocyanate and water, the isocyanurate of hexamethylene diisocyanate or the adduct of isophorone diisocyanate with trimethylolpropane. The average functionality can optionally be reduced by adding monoisocyanates. Examples of such chain terminating monoisocyanates are phenyl isocyanate, cyclohexyl isocyanate and stearyl isocyanate.

In order to ensure that the polyurethane resins used can be diluted with water, groups capable of forming anions must be incorporated into the polyurethane molecules. After neutralization, the groups capable of forming anions ensure that the polyurethane resin can be dispersed stably in water. The polyurethane resin should have an acid number of 10 to 60, preferably 20 to 35. The amount of groups capable of forming anions to be introduced into the polyurethane molecules can be calculated from the acid number.

Groups capable of forming anions are introduced into the polyurethane molecules via the Installation of connections (iii).

Compounds which contain two groups which are reactive toward isocyanate groups in the molecule are preferably used as component (iii). Suitable groups reactive toward isocyanate groups are in particular hydroxyl groups and primary and / or secondary amino groups. Suitable groups capable of forming anions are carboxyl, sulfonic acid and / or phosphonic acid groups, carboxyl groups being preferred. For example, alkanoic acids with two substituents on α-carbon atoms can be used as component (iii). The substituent can be a hydroxyl group, an alkyl group or preferably an alkylol group. These alkanoic acids have at least one, generally 1 to 3 carboxyl groups in the molecule. They have two to about 25, preferably 3 to 10, carbon atoms. Examples of component (iii) are dihydroxypropionic acid, dihydroxysuccinic acid and dihydroxybenzoic acid. A particularly preferred group of alkanoic acids are the α, α-dimethylolalkanoic acids of the general formula R⁴-C (CH₂OH) ₂COOH, where R⁴ represents a hydrogen atom or an alkyl group with up to about 20 carbon atoms. Examples of such compounds are 2,2-dimethylol acetic acid, 2,2-dimethylol propionic acid, 2,2-dimethylol butyric acid and 2,2-dimethylol pentanoic acid. The preferred dihydroxyalkanoic acid is 2,2-dimethylolpropionic acid. Compounds containing amino groups are, for example, α, δ-diaminovaleric acid, 3,4-diaminobenzoic acid, 2,4-diaminotoluenesulfonic acid and 2,4-diamino-diphenyl ether sulfonic acid.

The polyurethane resins used according to the invention can optionally also contain hydroxyl and / or Organic compounds containing amino groups with a molecular weight of 40 to 600, or a mixture of such compounds can be prepared (component (iv)). The use of component (iv) leads to an increase in the molecular weight of the polyurethane resins. As component (iv), for example, polyols with up to 20 carbon atoms per molecule, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butylene glycol, 1,6 -Hexanediol, trimethylolpropane, castor oil or hydrogenated castor oil, di-trimethylolpropane ether, pentaerythritol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, neopentylglycol, hydroxypivalic acid neopentylglycol esters, hydroxyethylated or hydroxypropylated bisphenol mixtures, and bisphenol ahydrogenated or hydroxypropylated bisphenol bisphenol be used.

The polyols are generally used in amounts of up to 30 percent by weight, preferably 2 to 20 percent by weight, based on the amount of components (i) and (iv) used. Di- and / or polyamines with primary and / or secondary amino groups can also be used as component (iv). Polyamines are essentially alkylene polyamines having 1 to 40 carbon atoms, preferably about 2 to 15 carbon atoms. They can carry substituents that have no hydrogen atoms that are reactive with isocyanate groups. Examples are polyamines with a linear or branched aliphatic, cycloaliphatic or aromatic structure and at least two primary amino groups. As diamines are hydrazine, ethylenediamine, propylenediamine, 1,4-butylenediamine, piperazine, 1,4-cyclohexyldimethylamine, 1,6-hexamethylenediamine, trimethylhexamethylenediamine, menthandiamine, isophoronediamine, 4,4'-diaminodicyclohexylmethane and aminoethylethanolamine. Preferred diamines are hydrazine, alkyl or cycloalkyl diamines, such as propylenediamine and 1-amino-3-amino-methyl-2,5,5-trimethylcyclohexane. It is also possible to use polyamines as component (iv) which contain more than two amino groups in the molecule. In these cases, however, care must be taken, for example by using monoamines, that no crosslinked polyurethane resins are obtained. Such useful polyamines are diethylenetriamine, triethylenetetramine, dipropylenetriamine and dibutylenetriamine. An example of a monoamine is ethylhexylamine.

With the aid of components (v), poly (oxyalkylene) groups can be introduced into the polyurethane molecules as nonionic stabilizing groups. As component (v) it is possible, for example, to use alkoxypoly (oxyalkylene) alcohols having the general formula R'0 - (- CH₂-CHR '' - 0-) _n H in the R 'for an alkyl radical having 1 to 6 carbon atoms, R''represents a hydrogen atom or an alkyl radical having 1 to 6 carbon atoms and n represents a number between 20 and 75.

The production of the polyurethane resins which can be used in combination with the polyacrylate resin essential to the invention is state of the art and is e.g. in US-PS 4,719,132, DE-OS-3 628 124, EP-A-89 497, EP-A-256 450 and WO 87/03829.

The water-dilutable polyester resins which can be used in combination with the polyacrylate resins essential to the invention can be prepared from polycarboxylic acids and polyols by generally well-known methods. Can be used to manufacture the polyester resins all starting materials listed in the description of component (i) are used.

• (α) Polyole oder ein Gemisch aus Polyolen und
• (β)Polycarbonsäuren oder Polycarbonsäureanhydride oder ein Gemisch aus Polycarbonsäuren und/oder Polycarbonsäureanhydriden zu einem Polyesterharz mit einem zahlenmittleren Molekulargewicht von 600 bis 5000, vorzugsweise 800 bis 2500, einer Säurezahl von 20 bis 70, vorzugsweise 25 bis 55 und einer Hydroxylzahl von 30 bis 200, vorzugsweise 45 bis 100 umgesetzt werden, wobei
  • die Komponenten (α) und (β) in einem molaren Verhältnis von 1,15 - 2,00 : 1, vorzugsweise 1,2 - 1,5 : 1 eingesetzt werden,
  • die Komponente (α) zu 30 bis 100 Mol-% aus aliphatischen Diolen besteht, die mindestens ein α C-Atom enthält, das sekundär, tertiär oder Glied eines kohlenstoffhaltigen Ringsystems ist und
  • die Komponente (β) zu 50 bis 100 Mol-% aus aromatischen und/oder cycloaliphatischen Polycarbonsäuren und zu 15 bis 40 Mol-% aus Tri- und/oder Tetracarbonsäuren besteht, wobei die Tri- und/oder Tetracarbonsäuren so eingesetzt werden, daß sie über mindestens zwei Carboxylgruppen in die Polyesterharzmoleküle eingebaut werden.

Polyester resins which are obtainable by. Are preferably used as water-dilutable polyester resins

• (α) polyols or a mixture of polyols and
• (β) polycarboxylic acids or polycarboxylic acid anhydrides or a mixture of polycarboxylic acids and / or polycarboxylic acid anhydrides to form a polyester resin with a number average molecular weight of 600 to 5000, preferably 800 to 2500, an acid number of 20 to 70, preferably 25 to 55 and a hydroxyl number of 30 to 200 , preferably 45 to 100 are implemented, wherein
  • components (α) and (β) are used in a molar ratio of 1.15-2.00: 1, preferably 1.2-1.5: 1,
  • component (α) consists of 30 to 100 mol% of aliphatic diols which contains at least one α C atom which is secondary, tertiary or member of a carbon-containing ring system and
  • component (β) consists of 50 to 100 mol% of aromatic and / or cycloaliphatic polycarboxylic acids and 15 to 40 mol% of tri- and / or tetracarboxylic acids, the tri- and / or tetracarboxylic acids being used so that they are incorporated into the polyester resin molecules via at least two carboxyl groups.

• (α1) 30 bis 100, vorzugsweise 50 bis 100 Mol-% aus aliphatischen Diolen, die mindestens ein α-C-Atom enthalten, das sekundär, tertiär oder Glied eines kohlenstoffhaltigen Ringsystems ist.
• (α2) 0 bis 20, vorzugsweise 0 bis 10 Mol-% aus aliphatischen Triolen und
• (α3) 0 bis 40, vorzugsweise 0 bis 20 Mol-% aus ethergruppenhaltigen Diolen.

Component (α) is too

• (α1) 30 to 100, preferably 50 to 100 mol% of aliphatic diols which contain at least one α-C atom which is secondary, tertiary or a member of a carbon-containing ring system.
• (α2) 0 to 20, preferably 0 to 10 mol% of aliphatic triols and
• (α3) 0 to 40, preferably 0 to 20 mol% of diols containing ether groups.

In principle, any aliphatic diol having 4 to 40, preferably 5 to 12 carbon atoms in the molecule in which at least one α-C atom is a secondary or tertiary C atom or a member in a carbon-containing ring system can be used as component (α1). Mixtures of such diols can also be used. Compounds which contain at least one molecular fragment of the general formula -C (R¹R²) -CH₂OH, where R¹ and R² are aliphatic, cycloaliphatic or aromatic hydrocarbon radicals having 1 to 20, preferably 1 to 6 carbon atoms, can be used, for example, as the (α1) component. Examples of such compounds are neopentyl glycol, 2-methyl-2-propylpropanediol-1,3, 2-ethyl-2-butylpropanediol-1,3, 2-ethyl-2-phenylpropanediol-1,3, 2,2,4 trimethylpentanediol 1,5, 2,2,5 Trimethylhexandiol 1,6 and Hydroxypivalinsäureneopentylglykolester called. Dimethylolcyclohexane is mentioned as an example of a compound in which at least one α-C atom is a member in a carbon-containing ring system. As component (α1) are preferably neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, dimethylolcyclohexane and 2-ethyl-2-butylpropanediol-1,3.

Glycerol, trimethylolpropane and trimethylolethane, for example, can be used as component (α2).

As component (α3) in particular those diols are used which contain 1 to 10 ether oxygen atoms in the molecule or mixtures of such compounds. Examples of component (α3) are: diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol and poly (ethylene oxide), poly (propylene oxide) and poly (ethylene oxide) (propylene oxide) with number-average molecular weights from 400 to 600.

• (β1) 50 bis 100, vorzugsweise 50 bis 80 Mol-% aus aromatischen und/oder cycloaliphatischen Polycarbonsäuren oder Mischungen aus solchen Polycarbonsäuren und
• (β2) 0 bis 50, vorzugsweise 20 bis 50 Mol.-% aus aliphatischen Polycarbonsäuren oder Mischungen aliphatischer Carbonsäuren,

wobei der Anteil an Tri- oder Tetracarbonsäuren 15 bis 40 Mol.-% beträgt. Anstelle der Carbonsäuren können selbstverständlich auch reaktive Carbonsäurederivate, wie z.B. Carbonsäureanhydride eingesetzt werden.Component (β) exists

• (β1) 50 to 100, preferably 50 to 80 mol% of aromatic and / or cycloaliphatic polycarboxylic acids or mixtures of such polycarboxylic acids and
• (β2) 0 to 50, preferably 20 to 50 mol% of aliphatic polycarboxylic acids or mixtures of aliphatic carboxylic acids,

wherein the proportion of tri- or tetracarboxylic acids is 15 to 40 mol%. Instead of the carboxylic acids, reactive carboxylic acid derivatives, such as carboxylic acid anhydrides, can of course also be used.

In principle, any cycloaliphatic or aromatic polycarboxylic acid having 5 to 30, preferably 6 to 18 carbon atoms in the molecule can be used as component (β1) or an anhydride of this polycarboxylic acid or a mixture of these polycarboxylic acids or their anhydrides. Examples of polycarboxylic acids that can be used are isophthalic acid, terephthalic acid, orthophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, 1,4 cyclohexanedicarboxylic acid, dicyclopentadiene dicarboxylic acid, trimesic acid (benzene-1,3,5-tricarboxylic acid), trimellitic acid, pyromellitic acid as well as their endomethyl hydride and endomethyl hydride. Isophthalic acid, terephthalic acid, orthophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, trimellitic acid, pyromellitic acid, their anhydrides or mixtures of these polycarboxylic acids or their anhydrides are preferably used as component (β1).

In principle, any linear or branched aliphatic polycarboxylic acid having 2 to 40 carbon atoms in the molecule or an anhydride of these polycarboxylic acids or a mixture of these polycarboxylic acids or their anhydrides can be used as component (β2). Examples of aliphatic polycarboxylic acids that can be used are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, polymerized fatty acids and citric acid and their anhydrides. Adipic acid, azelaic acid, sebacic acid, succinic acid, their anhydrides or mixtures of these polycarboxylic acids or their anhydrides are preferably used as component (β2). Polymerized, in particular dimerized, fatty acids are very particularly preferably used as component (β2). If polymerized fatty acids are used as component (β2), then basecoats with particularly good storage stability are obtained.

Polymeric fatty acids are generally prepared by polymerizing fatty acids, such as linolenic, linoleic or oleic acid individually, in a mixture or in a mixture with saturated fatty acids. A mixture is formed which, depending on the reaction procedure, contains mainly dimeric, but also monomeric and trimeric molecules as well as by-products. It is usually purified by distillation. Commercially available polymeric fatty acids generally contain at least 80% by weight of dimeric fatty acids, up to 20% by weight of trimeric fatty acids and a maximum of 1% by weight of monomeric fatty acids. It is preferred to use as component (β2) polymeric fatty acids which consist of at least 98% by weight of dimeric fatty acids and at most 2% by weight of trimeric fatty acids and at most traces of monomeric fatty acids.

Polymeric fatty acids contain both cyclic and linear aliphatic molecular fragments. For the purposes of the present inventions, however, they are not regarded as cycloaliphatic, but rather as linear aliphatic polycarboxylic acids and should therefore be added to component (β2).

Trimellitic acid or pyromellitic acid, their mixtures or their anhydrides are preferably used as tri- or tetracarboxylic acids.

The water-dilutable polyester resins are prepared by generally well-known methods in polyester chemistry by reacting components (α) and (β). The reaction temperature should advantageously be 140 to 240, preferably 180 to 220 ° C. In some cases it may be appropriate to catalyze the esterification reaction. Examples of useful catalysts are tetrabutyl titanate, Zinc octoate, tin octoate, dibutyltin oxide, organic salts of dibutyltin oxide, etc. When esterifying, care must be taken that the tri- or tetracarboxylic acids are incorporated into the polyester resin molecules in such a way that at least two carboxyl groups are esterified on statistical average.

Ammonia and / or amines (in particular alkylamines), amino alcohols and cyclic amines such as di- and triethylamine, dimethylaminoethanolamine, diisopropanolamine, morpholine, N-alkylmorpholine etc. can be used to neutralize the polyester resins. Volatile amines are preferred for neutralization.

The aminoplast resins which can be used in combination with the polyacrylate resins essential to the invention are offered by many companies as sales products (for example Cymel ^R from American Cyanamid Company, Resimene ^{R from} the Monsanto Company and Luwipal ^R from BASF AG). As a rule, these are at least partially etherified condensation products from compounds containing amino groups, in particular melamine or benzoguanamine and aldehydes, in particular formaldehyde. The water dilutability of the aminoplast resins generally depends on the degree of condensation and the etherification component. The lower the degree of condensation and the shorter the alkyl groups in the etherification component, the better the water-dilutability of the aminoplast resins. The water-dilutability of aminoplast resins can also be improved by introducing carboxyl groups (eg etherification with hydroxycarboxylic acids). In addition, the water-thinnability of aminoplast resins can be improved by adding water-thinnable solvents such as glycol ether.

In addition to the binders described above, the basecoats of the invention may also contain further water-dilutable synthetic resins which serve to grind the pigments and / or as rheology-controlling additives. Examples of such synthetic resins are: polyethers, e.g. Polypropylene glycol with a number average molecular weight of 400 to 900, water-soluble cellulose ethers, such as hydroxyethyl cellulose, methyl cellulose or carboxymethyl cellulose, and synthetic polymers with ionic and / or associative groups, such as polyvinyl alcohol, poly (meth) acrylamide, poly (meth) acrylic acid, polyvinyl pyrrolidone, styrene Maleic anhydride or ethylene-maleic anhydride copolymers and their derivatives or also hydrophobically modified ethoxylated urethanes or polyacrylates containing carboxyl groups.

The basecoats of the invention can also contain crosslinked polymicroparticles such as those e.g. disclosed in EP-A-38127.

The basecoats of the invention can also contain inorganic rheology control agents such as e.g. Layered silicates included.

As pigments, the basecoats according to the invention can contain coloring pigments based on inorganic materials, such as titanium dioxide, iron oxide, carbon black, etc., and / or coloring pigments based on organic substances and / or conventional metal pigments (eg commercially available aluminum bronzes, stainless steel bronzes ...) and / or non- metallic effect pigments (eg pearlescent or interference pigments) contain. The basecoats according to the invention preferably contain metal pigments and / or effect pigments. The level of pigmentation is normal Areas.

The basecoats of the invention generally have a solids content of about 15 to 50% by weight at spray viscosity. The solids content varies with the intended use of the basecoats. For metallic paints, for example, it is preferably 17 to 25% by weight. For plain-colored paints it is higher, for example 30 to 45% by weight.
The basecoats of the invention can additionally contain customary organic solvents. Their share is kept as low as possible. For example, it is below 15% by weight.

The basecoats of the invention are generally adjusted to a pH between 6.5 and 9.0. The pH can be adjusted with conventional amines, e.g. Triethylamine, dimethylaminoethanol and N-methylmorpholine can be adjusted.

The basecoats of the invention can be used both in series and in refinishing. They are preferably used for series painting.

Lacquers based on organic solvents, water-thinnable lacquers and also powder lacquers can be used as transparent topcoats. The varnishes can be used as unpigmented clear varnishes or as transparent pigmented varnishes.

With the basecoats of the invention, high-quality finishes can be produced even without overcoating with a transparent topcoat. In this way, single-layer paintwork is obtained, which is characterized by a particularly high Highlight gloss.

The paints according to the invention can be applied to any substrates, such as e.g. Metal, wood, plastic or paper can be applied.

The invention is explained in more detail in the following examples.
All information on parts and percentages are by weight, unless expressly stated otherwise.

A. Production of polyacrylate resins to be used according to the invention

32 parts by weight of butylglycol are placed in a steel kettle equipped with monomer feed, initiator feed, thermometer, oil heating and reflux condenser and heated to 110.degree.
A solution of 1.56 parts by weight of t-butyl perethylhexanoate in 3.5 parts by weight of butyl glycol is then added at a rate such that the addition after 1 h 30 min. is completed. At the beginning of the addition of the t-butyl perethylhexanoate solution, the addition of a mixture of (a1): 5.6 parts by weight of acrylic acid and (a2): 3.1 parts by weight of butyl methacrylate, 1.96 parts by weight of methyl methacrylate and 3.93 parts by weight of lauryl methacrylate and 1.96 parts by weight of styrene.
The mixture of (a1) and (a2) is added at such a rate that the addition is complete after 1 h.
After the t-butyl perethylhexanoate solution has been added completely, the polymerization temperature is kept at 110 ° C. for a further 30 minutes.
Then a solution of 6.0 parts by weight of t-butyl perethylhexanoate in 6.0 parts by weight of butyl glycol is added at such a rate that the addition after 5 h 30 min. is completed.
At the beginning of the addition of the t-butyl perethylhexanoate solution, the addition of a mixture of (b1): 21.6 parts by weight of n-butyl methacrylate, 20.0 parts by weight of methyl methacrylate and 20.0 parts by weight of lauryl methacrylate, ( b2): 20.4 parts by weight of hydroxypropyl acrylate and (b3): 15.0 parts by weight of styrene started. The mixture of (b1), (b2) and (b3) is added at such a rate that the addition is completed in 5 hours.
The temperature is still 1 h 30 min. kept at 110 ° C. The resin solution thus obtained is concentrated by distillation under vacuum to 80% by weight (solids content) and with dimethylethanolamine at about 80 ° C. within about 30 minutes. neutralized up to a degree of neutralization of 80%. The resin solution is cooled to 60 ° C and the heating is switched off.
Then enough water is slowly added until the solids content of the dispersion is about 40% by weight.
The dispersion obtained has the following characteristics: acid number 32.8 mg KOH / g, hydroxyl number: 80, number average molecular weight: 4990, particle size 221 nm 1
¹ measured with laser light scattering, measuring device: Malvern Autosizer 2C.

A 2

In a steel kettle equipped with monomer feed, initiator feed, thermometer, oil heating and reflux condenser, 35.8 parts by weight of butylglycol are placed in and on Heated to 110 ° C. Then a solution of 3.5 parts by weight of t-butyl perethylhexanoate in 7.0 parts by weight of butyl glycol is added at such a rate that the addition after 5 h 30 min. is completed.
With the beginning of the addition of the t-butyl perethylhexanoate solution, the addition of (a1): 5.0 parts by weight of acrylic acid is also started. (a1) is added at such a rate that the addition after 20 min. is completed. After (a1) has been added completely, a mixture of (b1): 22.0 parts by weight of n-butyl acrylate, 20.0 parts by weight of t-butyl acrylate and 15.0 parts by weight of methyl methacrylate, (b2 ): 23.0 parts by weight of hydroxypropyl acrylate and (b3): 15.0 parts by weight of styrene started. The mixture of (b1), (b2) and (b3) is added at such a rate that the addition after 4 h 50 min. is completed.
After the mixture of (b1), (b2) and (b3) has been added completely, the temperature is raised for a further 1 h 50 min. kept at 110 ° C.
The resin solution thus obtained is cooled to 80 ° C. and with dimethylethanolamine at approx. 80 ° C. within approx. 30 min. neutralized up to a degree of neutralization of 82.5%. The resin solution is cooled to 60 ° C and the heating is switched off.
Then enough water is slowly added until the solids content of the dispersion is about 40% by weight.
The dispersion obtained has the following key figures: acid number 33.5 mg KOH / g, hydroxyl number: 100, particle size: 267, solids content (in% by weight, 1 h at 130 ° C.): 40.0.

B. Production of a polyacrylate resin not according to the invention

35.8 parts by weight of butylglycol are placed in a steel kettle equipped with monomer feed, initiator feed, thermometer, oil heating and reflux cooler and heated to 110.degree. Then a solution of 3.5 parts by weight of t-butyl perethylhexanoate in 7.0 parts by weight of butyl glycol is added at such a rate that the addition after 5 h 30 min. is completed.
At the beginning of the addition of the t-butyl perethylhexanoate solution, a mixture of 22.0 parts by weight of n-butyl acrylate, 20.0 parts by weight of t-butyl acrylate, 15.0 parts by weight of methyl methacrylate, 15.0 is also added Parts by weight of styrene, 23.0 parts by weight of hydroxypropyl acrylate and 5.0 parts by weight of acrylic acid started.
The monomer mixture is added at such a rate that the addition after 5 h 10 min. is completed.
Further procedure analogous to A 2.
The dispersion obtained has the following key figures: acid number: 39.0 mg KOH / g, hydroxyl number: 100, solids content (in% by weight, 1 h at 130 ° C.): 40.0.

C. Preparation of an aqueous polyurethane resin dispersion

569 parts by weight of a condensation product (number average molecular weight: 1460) from 1 mol of a polymeric fatty acid (dimer content at least 98% by weight, trimers content at most 2% by weight, monomer content at most traces), 1 mol of isophthalic acid and 2.626 mol of hexanediol, 46 Parts by weight of dimethylolpropionic acid, 7 parts by weight of neopentyl glycol, 420 parts by weight of methyl ethyl ketone and 213 parts by weight of isophorone diisocyanate are mixed in a temperable part Isophorone diisocyanate is heated to 80 ° C. in a temperature-controlled reaction vessel provided with a stirrer and water separator under a nitrogen atmosphere. The reaction is continued up to an NCO content of 1.0% by weight, based on the total composition.
Then 24 parts by weight of trimethylolpropane are added and the mixture is stirred at 80 ° C. until no more isocyanate groups can be detected.
Then 25.8 parts by weight of dimethylethanolamine and then 2552 parts by weight of deionized water are slowly stirred in. The methyl ethyl ketone is distilled off under vacuum.
A finely divided dispersion with a pH of 7.8, a non-volatile content of 27% by weight and an acid number of 25 mg KOH / g is obtained.

D. Preparation of an aqueous polyester resin dispersion

In a reactor equipped with a stirrer, a thermometer and a packed column, 729 parts by weight of neopentyl glycol, 827 parts by weight of hexanediol, 462 parts by weight of hexahydrophthalic anhydride and 1710 parts by weight of a polymeric fatty acid (at least dimer content 98% by weight, trimer content at most 2% by weight, monomer content at most traces) and weighed and melted. The mixture is heated with stirring so that the column top temperature does not exceed 100.degree. At max. Esterified 220 ° C until an acid number of 8.5 is reached. After cooling to 180 ° C., 768 parts by weight of trimellitic anhydride are added and further esterification is carried out until an acid number of 30 is reached. The mixture is then cooled to 120 ° C. and dissolved in 1410 parts by weight of butanol. After cooling to 90 ° C slowly 16.2 parts by weight of dimethylethanolamine and then 1248 parts by weight of deionized water were stirred in. A finely divided dispersion having a pH of 7.8, a nonvolatile content of 60% by weight and an acid number of 30 mg KOH / g is obtained.

E. Preparation of an Aqueous Metallic Basecoat (Comparative Example)

33.5 parts by weight of thickener (paste of a sodium magnesium silicate with a layer structure *, 3% strength in water) are introduced.
A solution of 4.3 parts by weight of butyl glycol and 6.0 parts by weight of a 90% solution of a commercially available water-dilutable melamine-formaldehyde resin in isobutanol (Cymel 327® 1) is added with stirring. Then 33.3 parts by weight of the PU dispersion according to C and 0.4 parts by weight of dimethylethanolamine solution (10% in H₂O) are added to this mixture with stirring. An aluminum pigment slurry is prepared separately as follows: 4.4 parts by weight of a commercially available chromated aluminum paste (65% in petrol / solvent naphtha / butyl glycol, average particle diameter: 15 µm) are homogenized with the addition of 4 parts by weight of butyl glycol. 6.4 parts by weight of the water-soluble polyester resin according to D and 1.0 part by weight of polypropylene glycol (number average molecular weight: 900) are then added to this slurry.
This aluminum pigment slurry is stirred into the mixture described above. Then 6.7 parts by weight of deionized water are added and a pH of 7.65-7.85 is established with dimethylethanolamine solution (10% in water).
* Laponite RD
®¹ commercial product from American Cyanamid Company

F. Preparation of an Aqueous Metallic Basecoat According to the Invention

33.5 parts by weight of thickener (paste of a sodium magnesium silicate with a layer structure *, 3% strength in water) are introduced.
A solution of 4.3 parts by weight of butylglycol and 6.0 parts by weight of a 90% solution of a commercially available water-dilutable melamine-formaldehyde resin in isobutanol (Cymel 327®) is added with stirring. Then 33.3 parts by weight of the PU dispersion according to C, 0.4 parts by weight of dimethylethanolamine solution (10% in water) and 4.8 parts by weight of the polyacrylate resin dispersion according to A 1 are added to this mixture in succession with stirring. An aluminum pigment slurry is prepared separately as follows: 4.4 parts by weight of a commercially available chromated aluminum paste (65% in petrol / solvent naphtha / butylglycol, average particle diameter: 15 µm) are homogenized with the addition of 4 parts by weight of butylglycol. 3.2 parts by weight of the water-soluble polyester resin according to D and 1.0 part by weight of polypropylene glycol (number average molecular weight: 900) are then added to this slurry. This aluminum pigment slurry is stirred into the mixture described above. Then 3.8 parts by weight of deionized water are added and the pH is adjusted to 7.65-7.85 with dimethylethanolamine solution (10% in water).
* Laponite RD

G. Application and testing of the aqueous metallic basecoats

The aqueous metallic basecoats prepared in accordance with E and F are adjusted to an application solid of 24.2% by weight with distilled water and applied to a phosphated steel sheet coated with a commercially available electrodeposition coating and a commercially available filler such that a dry film thickness of 12-15 µm is obtained. The applied basecoats are 10 min. at room temperature and 10 min. dried at 80 ° C in a forced air oven. Then a commercially available 2-component clear lacquer based on polyacrylate / polyisocyanate is applied, then the product is briefly flashed off and 20 min. baked in a convection oven at 140 ° C. Test results: Basecoat according to E Basecoat according to F L 25 ° (1) 101.7 102.2 L 70 ° (1) 40.4 40.9 Gloss (2) 83 84 DOI (3) 92 92 Cross cut (4) 0 0 KK gloss (5) 81 81 Cross cut 1 1 according to KK DOI according to KK 91 91 1) Color fraction L * according to DIN 6174 determined with the goniospectrophotometer from Zeiss. 2) Degree of gloss according to DIN 67530, angle 20 ° 3) Distinctness of Reflected Image: If the surface to be assessed is illuminated below 30 °, the direct reflection is measured at a gloss angle of -30 ° and in the immediate vicinity of the gloss angle at -30 ° ± 0.3 °. The DOI value determined from this corresponds to the visually perceived sharpness of the mirror image of an object on this surface. The DOI value is also called the sharpness value. Measured values: 100 best value; 0 worst value. 4) Testing according to DIN 53151 including tesa tear test. 5) 240 h at 40 ° C KK (according to DIN 50017)

Testing the viscosity stability under shear stress

To test the viscosity stability under shear stress, clear lacquer extracts (clear lacquer extract = basecoat without pigments) of the basecoats according to E and F were stirred vigorously for 1 hour using a blade stirrer and then sheared and measured in a viscometer with a shear gradient of 0 to 50 s ⁻¹. The clear lacquer extract of the basecoat according to E showed a viscosity drop of approx. 40%. The clear lacquer extract of the basecoat according to F, however, showed only a drop in viscosity of less than 10%. This slight drop in viscosity has no negative effects on the application behavior and the settling behavior.

H. Preparation of a pigment paste for aqueous solid basecoats

10 parts by weight of thickener (paste of a sodium magnesium silicate with a layer structure, 3% strength in water) are initially introduced: 4.5 parts by weight are added with stirring Dimethylethanolamine solution (10% in water), 2 parts by weight of polypropylene glycol (molecular weight 900), 46.70 parts by weight of the polyester resin according to D and 23.35 parts by weight of deionized water were added. The following pigments are then added individually and stirred in: 2.65 parts by weight of Irgazin Rot DPP BO®¹, 4.38 parts by weight of Cromophthalrot A2B®¹, 5.29 parts by weight of Novoperm Orange H2 70®² and 1 , 13 parts by weight of Sicotan Yellow 2 1912®³. Finally the mixture is 20 min. homogenized under a conventional laboratory dissolver.
It is then ground on a conventional laboratory bead mill to a grain size according to Hegmann (ISO 152) of ≦ 5 µm.
The pH value of the pigment paste should be between 8 - 8.5, otherwise it is adjusted to this value with a dimethylethanolamine solution (10% in water).

I. Production of aqueous solid basecoats

Using the pigment paste and the ingredients listed below, two plain basecoats are produced, plain basecoat 2 being a comparative example. In both basecoats, the weight ratio of pigment to solid resin and the weight ratio of OH-containing solid resin to melamine formaldehyde resin are the same.
®¹ commercial product from Ciba Geigy
®² trading product from Hoechst AG
®³ commercial product from BASF AG

Uni basecoat 1 Uni basecoat 2 Pigment paste: 41.33 33.57 Polyacrylate resin according to A 2 25.77 - Polyacrylate resin according to B - 20.90 Luwipal LR 8789 5.88 4.77 Resimene 4518 0.92 0.75 deionized 26.10 40.01 water

The above Ingredients are mixed in succession with stirring. The figures are parts by weight. The basecoats thus obtained are adjusted to a viscosity of 28 s (DIN 4). Uni basecoat 1 at this viscosity has a solids content of 35% by weight (1 h, 130 ° C) and Uni basecoat 2 has a solids content of 28.3% by weight (1 h, 130 ° C).

J. Application and testing of the uni basecoats

After 48 hours of storage, the aqueous plain basecoats produced according to I. are applied to phosphated steel sheets coated with a commercially available electrodeposition coating and a commercially available filler: pneumatic spray application at a relative atmospheric humidity of 60% and a temperature of 23 ° C. using a pressure vessel , two coats, with 2 minutes intermediate drying after the first application, 1 minute after the second application and 10 minutes drying at 80 ° C in a convection oven. Then a commercial clear coat based on polyacrylate / melamine formaldehyde resin applied, briefly flashed off and baked at 130 ° C for 30 minutes.

The examination of the two-layer coating obtained in this way gave the following results: Two-coat painting with solid basecoat 1 Two-coat painting with solid basecoat 2 VDA¹ rockfall 2nd 2-3 Cross cut 0 0 Gloss 20 ° 87 87 Cooker limit² 45 µm 28 µm Runner limit³ 45 µm 24 µm ¹ VDA: Association of the German automotive industry; Bombardment medium: 1000 g angular blasting agent; Grain size: 4 - 5 mm; Pressure: 1.5 bar; VDA stone chip device 508 ² application according to the described method; Basecoat thicknesses where stove bubbles appear ³ Application according to the described method; Basecoat thicknesses where runners are formed when applied to vertical perforated boards and then predried in the vertical position in the basecoat.

Claims (9)

1. Process for the production of a multicoat protective and/or decorative finish in which

   (1) an aqueous pigmented basecoat is applied to the substrate surface as basecoat,

   (2) a polymer film is formed from the paint applied in stage (1),

   (3) a transparent topcoat is applied to the basecoat obtained in this way and subsequently

   (4) the basecoat is baked together with the topcoat,

   characterized in that the basecoat comprises a water-thinnable polyacrylate resin which can be obtained by adding, either consecutively or alternately in part amounts,

   (I)

   (a1) 2.5 to 15, preferably 3 to 7% by weight of an ethylenically unsaturated monomer which contains at least one carboxyl group per molecule and is copolymerizable with (b1), (b2), (b3) and (a2), or a mixture of such monomers, together with

   (a2) 0 to 60, preferably 0 to 28% by weight of an ethylenically unsaturated monomer which is free from carboxyl groups and is copolymerizable with (b1), (b2), (b3) and (a1), or a mixture of such monomers, and

   a component (b), consisting of

   (b1) 40 to 90, preferably 40 to 80% by weight of a (meth)acrylic acid ester which is copolymerizable with (b2), (b3), (a1) and (a2) and is essentially free from carboxyl groups, or a mixture of such (meth)acrylic acid esters and

   (b2) 0 to 45, preferably 4 to 34% by weight of an ethylenically unsaturated monomer which is copolymerizable with (b1), (b3), (a1) and (a2), contains at least one hydroxyl group per molecule and is essentially free from carboxyl groups, or a mixture of such monomers, and

   (b3) 0 to 40, preferably 10 to 30% by weight of an ethylenically unsaturated monomer which is copolymerizable with (b1), (b2), (a1) and (a2), is essentially free from carboxyl groups and is different from (b1) and (b2), or a mixture of such monomers,

   to an organic solvent or solvent mixture and carrying out a polymerization in the presence of at least one polymerization initiator and

   (II) at the end of the polymerization neutralizing, at least partially, the resultant polyacrylate resin and dispersing it in water, the sum of the proportions by weight of (a1), (a2), (b1), (b2) and (b3) always being 100% by weight, and the type and amount of (b1), (b2), (b3), (a1) and (a2) being chosen so that the polyacrylate resin has a hydroxyl value of 0 to 200, preferably of 20 to 120, an acid value of 20 to 100, preferably of 25 to 50, and a glass transition temperature (T_G) of -40°C to +60°C, preferably of -20°C to +40°C.
2. Aqueous pigmented paint, comprising a water-thinnable polyacrylate resin which can be obtained by adding, either successively or alternately in part amounts,

   (I)

   (a1) 2.5 to 15, preferably 3 to 7% by weight of an ethylenically unsaturated monomer which contains at least one carboxyl group per molecule and is copolymerizable with (b1), (b2), (b3) and (a2), or a mixture of such monomers, together with

   (a2) 0 to 60, preferably 0 to 28% by weight of an ethylenically unsaturated monomer which is free from carboxyl groups and is copolymerizable with (b1), (b2), (b3) and (a1), or a mixture of such monomers, and

   a component (b), consisting of

   (b1) 40 to 90, preferably 40 to 80% by weight of a (meth)acrylic acid ester which is copolymerizable with (b2), (b3), (a1) and (a2) and is essentially free from carboxyl groups, or a mixture of such (meth)acrylic acid esters, and

   (b2) 0 to 45, preferably 4 to 34% by weight of an ethylenically unsaturated monomer which is copolymerizable with (b1), (b3), (a1) and (a2), contains at least one hydroxyl group per molecule and is essentially free from carboxyl groups, or a mixture of such monomers, and

   (b3) 0 to 40, preferably 10 to 30% by weight of an ethylenically unsaturated monomer which is copolymerizable with (b1), (b2), (a1) and (a2), is essentially free from carboxyl groups and is different from (b1) and (b2), or a mixture of such monomers,

   to an organic solvent or solvent mixture and carrying out a polymerization in the presence of at least one polymerization initiator and,

   (II) at the end of the polymerization, neutralizing, at least partially, the resultant polyacrylate resin and dispersing it in water, the sum of the proportions by weight of (a1), (a2), (b1), (b2) and (b3) always being 100% by weight and the type and amount of (b1), (b2), (b3), (a1) and (a2) being chosen so that the polyacrylate resin has a hydroxyl value of 0 to 200, preferably of 20 to 120, an acid value of 20 to 100, preferably of 25 to 50, and a glass transition temperature (T_G) of -40°C to +60°C, preferably of -20°C to +40°C.
3. Process or paint according to Claim 1 or 2, characterized in that the basecoat contains a metallic pigment or a mixture of metallic pigments.
4. Process or paint according to any one of Claims 1 to 3, characterized in that the basecoat or the paint comprises, in addition to the water-thinnable polyacrylate resin, a water-thinnable polyurethane resin and/or a water-thinnable polyester resin and/or a water-thinnable amino resin.
5. Process or paint according to any one of Claims 1 to 4, characterized in that the basecoat or the paint comprises a non-metallic pigment or a mixture of non-metallic pigments and a mixture of

   (A) 10 to 95, preferably 25 to 70% by weight of the water-thinnable polyacrylate resin,

   (B) 5 to 50, preferably 10 to 40% by weight of an amino resin,

   (C) 0 to 85, preferably 20 to 60% by weight of a water-thinnable polyester resin and

   (D) 0 to 85, preferably 0 to 40% by weight of a water-thinnable polyurethane resin,

   the percentages by weight of the components (A) to (D) always totalling 100.
6. Process or paint according to any one of Claims 1 to 5, characterized in that the basecoat or the paint comprises a metallic pigment and a mixture of

   (A) 0.1 to 60, preferably 1 to 30% by weight of the water-thinnable polyacrylate resin,

   (B) 0 to 50, preferably 5 to 30% by weight of an amino resin,

   (C) 0 to 50, preferably 15 to 40% by weight of a water-thinnable polyester resin and

   (D) 10 to 99.9, preferably 20 to 60% by weight of a water-thinnable polyurethane resin,

   the percentages by weight of the components (A) to (D) always totalling 100.
7. Process or paint according to any one of Claims 4 to 6, characterized in that the water-thinnable polyester resin can be obtained by reacting

   (α) polyols or a mixture of polyols and

   (β) polycarboxylic acids or polycarboxylic anhydrides, or a mixture of polycarboxylic acids and/or polycarboxylic anhydrides, to form a polyester resin having a number average molecular weight of 600 to 5000, preferably of 800 to 2500, an acid value of 20 to 70, preferably of 25 to 55, and a hydroxyl value of 30 to 200, preferably of 45 to 100, and the resultant polyester resin is neutralized, at least partially, in which reaction

   - the components (α) and (β) are used in a molar ratio of 1.15 - 2.00:1, preferably 1.2 - 1.5:1,

   - the component (α) consists of 30 to 100 mol% of aliphatic diols containing at least one α carbon atom which is secondary, tertiary or a member of a carbon-containing ring system, and

   - the component (β) consists of 50 to 100 mol% of aromatic and/or cycloaliphatic polycarboxylic acids and of 15 to 40 mol% of tricarboxylic and/or tetracarboxylic acids, the tricarboxylic and/or tetracarboxylic acids being used in such a way that they are incorporated in a statistical average in the polyester resin molecules via at least two carboxyl groups.
8. Process or paint according to Claim 7, characterized in that the component (β) consists of 50 to 80 mol% of aromatic and/or cycloaliphatic polycarboxylic acids and of 20 to 50 mol% of one or more polymeric fatty acids, polymeric fatty acids not being considered as cycloaliphatic polycarboxylic acids.
9. Use of the aqueous paint according to any one of Claims 2 to 8 as basecoat for the production of multicoat protective and/or decorative finishes of the basecoat/clearcoat type.